We have devised a new method for determining the heating effects of the electron beam on metal foils in a transmission electron microscope. Thin specimens of tin, lead, and zinc were melted in the electron microscope using the combination of heat from the electron beam in ’’normal’’ usage and a previously calibrated heating cartridge. The temperature rise due to the electron beam heating was the difference between the melting temperature of the metal foil and the ’’temperature contribution’’ of the heating element. For a given beam current the temperature rise of the metal foils due to be beam was determined to within ±10 °C using this technique. This technique appears to be valid provided the beam current is kept at the same constant value during calibration and operation.